1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method rotating a substrate such as a semiconductor wafer or a substrate for an optical disk for performing processing such as cleaning by supplying a processing solution such as a chemical solution or deionized water to the substrate and supplying gas such as inert gas such as nitrogen gas or dry air to the substrate after or during the processing for drying the substrate.
2. Description of the Background Art
FIG. 12 is a partially fragmented schematic front elevational view of a conventional substrate processing apparatus, FIG. 13 is a longitudinal sectional view of a principal part thereof, and FIG. 14 is a sectional view taken along the line XI-XI in FIG. 13. The apparatus illustrated in FIGS. 12 to 14 is a substrate processing apparatus of a single-substrate type performing cleaning processing with a chemical solution, rinse processing with deionized water and spin-drying processing on both of the upper and lower surfaces of a substrate.
This substrate processing apparatus comprises a spin chuck 100 horizontally holding and rotating a substrate such as a semiconductor wafer W, for example, and an atmosphere blocking member 102 arranged oppositely and proximately to the upper surface of the wafer W held by the spin chuck 100. The atmosphere blocking member 102 is in the form of a disc corresponding in planar size to the wafer W.
The spin chuck 100 is constituted of a discoidal spin base 104 holding the wafer W on its upper surface and a rotary cylinder 106 suspended from the central portion of the lower surface of the spin base 104. At least three chuck pins 108 for grasping the peripheral edge of the wafer W and holding the wafer W at a space from the upper surface of the spin base 104 are circumferentially uniformly distributed and embedded in the peripheral edge of the upper surface of the spin base 104. The spin base 104 also functions as an atmosphere blocking member arranged oppositely and proximately to the lower surface of the wafer W held by the same. A rotating/driving mechanism consisting of a motor 110, a driving pulley 112 fixed to the rotary shaft of the motor 100, a driven pulley 114 engaged with the outer peripheral surface of the rotary cylinder 106 and a belt 116 extended along the driving pulley 112 and the driven pulley 114 rotates the rotary cylinder 106 about a vertical axis. This rotation of the rotary cylinder 106 is followed by rotation of the wafer W and the spin base 104. A long, narrow cylindrical inner shaft 118 is inserted into the hollow portion of the rotary cylinder 106. The inner shaft 118 is fixedly uprighted and arranged coaxially with the rotary cylinder 106, while a bearing (not shown) is interposed between the outer peripheral surface of the inner shaft 118 and the inner peripheral surface of the rotary cylinder 106.
The atmosphere blocking member 102 is concatenated to the lower end of a rotary support cylinder 120. A long, narrow cylindrical inner shaft 122 is inserted into the hollow portion of the rotary support cylinder 120 similarly to the rotary cylinder 106 of the aforementioned spin chuck 100 although FIG. 12 illustrates no detailed structure, and this inner shaft 122 and the rotary support cylinder 120 are arranged coaxially with each other while a bearing (not shown) is interposed between the outer peripheral surface of the inner shaft 122 and the inner peripheral surface of the rotary support cylinder 120. The rotary support cylinder 120 is suspended from the forward end of a support arm 124 and supported to be rotatable by a motor 126 about a vertical axis. The motor 126 rotates the rotary support cylinder 120, thereby rotating the atmosphere blocking member 102 along with the rotary support cylinder 120. A vertical drive unit (not shown) consisting of a linear driving mechanism such as an air cylinder vertically reciprocates the rotary support cylinder 120 and the support arm 124. The atmosphere blocking member 102 approaches to and separates from the upper surface of the wafer W held on the spin base 104 due to the vertical reciprocation of the rotary support cylinder 120.
The inner shaft 122 inserted into the hollow portion of the rotary support cylinder 120 is formed on its axial portion with a processing solution supply passage 128 having a processing solution discharge port 130 on its lower end opposed to the upper surface of the wafer W held on the spin base 104. A space portion defined between the outer peripheral surface of the inner shaft 122 and the inner peripheral surface of the rotary support cylinder 120 constitutes a gas supply passage 132 having an annular gas discharge port 134 on its lower end. Similarly, the inner shaft 118 inserted into the hollow portion of the rotary cylinder 106 of the spin chuck 100 is formed on its axial portion with a processing solution supply passage 136 having a processing solution discharge port 138 on its upper end opposed to the lower surface of the wafer W held on the spin base 104. A space portion defined between the outer peripheral surface of the inner shaft 118 and the inner peripheral surface of the rotary cylinder 106 constitutes a gas supply passage 140 having an annular gas discharge part 142 on its upper end. The processing solution supply passages 128 and 136 are channel-connected to a processing solution supply part 144 supplying processing solutions such as a chemical solution and deionized water respectively. The gas supply passages 132 and 140 are channel-connected to a gas supply part 146 supplying process gas such as inert gas such as nitrogen gas or dry air respectively.
The aforementioned substrate processing apparatus performs processing in the following manner, for example: The substrate processing apparatus holds the wafer W on the spin base 104 of the spin chuck 100 and rotates the wafer W in a horizontal plane about a vertical axis. The processing solution supply part 144 supplies the chemical solution to the processing solution supply passages 128 and 136 so that the processing solution discharge ports 130 and 138 opening on the lower surface of the atmosphere blocking member 102 and the upper surface of the spin base 104 respectively discharge the chemical solution toward the central portions of the upper and lower surfaces of the wafer W respectively. The chemical solution discharged toward the central portions of the upper and lower surfaces of the wafer W is spread entirely over the wafer W due to centrifugal force following the rotation of the wafer W for cleaning the upper and lower surfaces of the wafer W.
When completely cleaning the wafer W with the chemical solution, the substrate processing apparatus switches the chemical solution supplied from the processing solution supply part 144 to the processing solution supply passages 128 and 136 to the deionized water, which in turn is discharged from the processing solution discharge ports 130 and 138 toward the central portions of the upper and lower surfaces of the wafer W respectively. The deionized water discharged toward the central portions of the upper and lower surfaces of the wafer W is spread entirely over the wafer W due to the centrifugal force following the rotation of the wafer W for rinsing the upper and lower surfaces of the wafer W. In the aforementioned cleaning processing with the chemical solution and/or the rinse processing with the deionized water, the substrate processing apparatus supplies process gas such as nitrogen gas from the gas supply part 146 to the gas supply passages 132 and 140 at need for discharging the process gas from the annular gas discharge ports 134 and 142 opening on the lower surface of the atmosphere blocking member 102 and the upper surface of the spin base 104 respectively toward the upper and lower surfaces of the wafer W respectively.
When completely rinsing the wafer W with the deionized water, the substrate processing apparatus stops discharging the deionized water from the processing solution discharge ports 130 and 138 and supplies the process gas from the gas supply part 146 to the gas supply passages 132 and 140. The substrate processing apparatus discharges the process gas from the annular gas discharge ports 134 and 142 toward the upper and lower surfaces of the wafer W respectively while rotating the wafer W for draining the deionized wafer remaining on the upper and lower surfaces of the wafer W from the peripheral edge of the wafer W due to the centrifugal force following the rotation of the wafer W thereby drying the upper and lower surfaces of the wafer W respectively. At this time, the process gas discharged from the gas discharge ports 134 and 142 toward the upper and lower surfaces of the wafer W respectively flows along the upper and lower surfaces of the wafer W respectively and is spread entirely over the wafer W for prompting drying of the wafer W.
Japanese Patent Application Laying-Open Gazette No. 11-274135 (1999) discloses a substrate processing apparatus having a processing solution discharge part and a gas discharge part different in structure from those shown in FIGS. 13 and 14. FIG. 16 is a longitudinal sectional view of a principal part of the substrate processing apparatus described in the aforementioned literature, and FIG. 17 is a sectional view taken along the line XIV-XIV in FIG. 16. As shown in FIGS. 16 and 17, an inner shaft 152 inserted into the hollow portion of a rotary support cylinder 150 concatenated with an atmosphere blocking member 148 on its lower end is formed with a gas supply passage 154 to be uncoaxial with the inner shaft 152. The atmosphere blocking member 148 is formed on its surface (lower surface) opposed to the upper surface of a wafer W held on a spin base 164 of a spin chuck 162 with a gas discharge port 156, which is eccentric to the wafer W. The inner shaft 152 is also formed with a processing solution supply passage 158 parallel to the gas supply passage 154, while the atmosphere blocking member 148 is formed on its surface opposed to the upper surface of the wafer W with a processing solution discharge port 160 adjacently to the gas discharge port 156.
Similarly, an inner shaft 168 inserted into the hollow portion of a rotary cylinder 166 of the spin chuck 162 is formed with a gas supply passage 170 to be uncoaxial with the inner shaft 168, and the spin base 164 is formed on its upper surface opposed to the lower surface of the wafer W held by the same with a gas discharge port 172 eccentrically to the wafer W. The inner shaft 168 is also formed with a processing solution supply passage 174 parallel to the gas supply passage 170, while the spin base 164 is formed on its upper surface with a processing solution discharge port 176 adjacently to the gas discharge port 172.
The aforementioned substrate processing apparatuses dry the wafer W by spin drying. In this case, droplets remaining on the wafer W not yet dried by high-speed rotation are scattered on the surface of the wafer W in high-speed rotation to cause formation of watermarks or adhesion of particles to the wafer W leading to a device failure or reduction of the yield. Droplets adhering to and remaining on the surface (lower surface) of the atmosphere blocking member 102 opposed to the wafer W also cause formation of watermarks or adhesion of particles.
Therefore, it is important to spin-dry the wafer W by high-speed rotation while completely expelling droplets from the wafer W and the lower surface of the atmosphere blocking member 102. Particularly when the substrate processing apparatus performs drying processing while approximating the atmosphere blocking member 102 to the wafer W held on the spin base 104, it is necessary to efficiently expel droplets remaining on the wafer W after the rinse processing while approximating the atmosphere blocking member 102 to the wafer W before spin-drying the wafer W by high-speed rotation.
In the conventional substrate processing apparatus shown in FIGS. 13 and 14, the gas discharge port 134 of the atmosphere blocking member 102 is annularly formed around the rotation center of the wafer W to enclose the processing solution discharge port 130 opposed to the central portion of the wafer W, for homogeneously discharging the process gas from the periphery of the processing solution discharge port 130. The spin base 104 serving as an atmosphere blocking member oppositely to the lower surface of the wafer W also has a similar structure. The substrate processing apparatus generally discharges the chemical solution or the deionized water from the processing solution discharge ports 130 and 138 toward the central portion of the wafer W while discharging the process gas such as nitrogen gas toward the central portion of the wafer W from the gas discharge ports 134 and 142 in the cleaning processing with the chemical solution or the rinse processing with the deionized water, and discharges only the process gas toward the central portion of the wafer W in the drying processing.
When the substrate processing apparatus having the structure shown in FIGS. 13 and 14 discharges the process gas toward the central portion of the wafer W from the gas discharge ports 134 and 142 in the drying processing, the process gas flows around the center of the wafer W as shown in FIG. 15 (while FIG. 15 shows only the upper surface of the wafer W, this also applies to the lower surface of the wafer W). The process gas discharged from the annular gas discharge port 134 toward the central portion of the wafer W forms a flow directed toward the center C of the wafer W in addition to a flow directed toward the periphery of the wafer W, as shown by broken lines in FIG. 15. The flow of the process gas directed from the annular periphery toward the center C of the wafer W inhibits droplets remaining on the central portion of the wafer W from centrifugal expulsion toward the periphery. In particular, droplets readily remain on the central portion of the wafer W due to smaller centrifugal force acting thereon as compared with that on the periphery. Consequently, drying is retarded on the central portion of the wafer W or droplets remaining on the central portion are scattered in high-speed rotation of the wafer W, to cause the aforementioned formation of watermarks or adhesion of particles.
In the substrate processing apparatus having the structure shown in FIGS. 16 and 17 disclosed in Japanese Patent Application Laying-Open Gazette No. 11-274135, process gas discharged from the gas discharge port 156 to a position deviating from the center C of the wafer W forms a powerful flow directed toward the center C of the wafer W as shown by a broken line in FIG. 18 (while FIG. 18 shows only the upper surface of the wafer W, this also applies to the lower surface of the wafer W), thereby expelling droplets remaining on the central portion of the wafer W toward the periphery.
Thus, the substrate processing apparatus having the structure shown in FIGS. 16 and 17 is extremely effective for preventing a liquid from remaining on the central portion of the wafer W. In this apparatus, however, it is difficult to remove droplets from the periphery of the wafer W with the process gas. While it is necessary to discharge the process gas from the gas discharge port 156 toward the central portion of the wafer W at a large flow rate in order to remove droplets from the periphery of the wafer W with the process gas, the droplets are scattered to readily adhere to the lower surface of the atmosphere blocking member 148 in this case, and it follows that the substrate processing apparatus uses the process gas beyond necessity. The range where the substrate processing apparatus can remove droplets from the wafer W by discharging the process gas toward the central portion of the wafer W is so limited that it is extremely difficult to completely remove droplets from the periphery of the wafer W with the process gas particularly when the wafer W has a large diameter of 300 mm. Thus, the substrate processing apparatus having the structure shown in FIGS. 16 and 17 cannot completely expel droplets remaining on the wafer W before spin-drying the wafer W by high-speed rotation either. Therefore, it is impossible to effectively prevent the aforementioned formation of watermarks or adhesion of particles to the wafer W.